JPWO2017138321A1 - Image display device, in-vehicle system, and image display method - Google Patents

Abstract

  An image display device includes: a light source that emits light; a light scanning unit that draws a display image by scanning a predetermined scanning region with light from the light source; and a light amount detection unit that detects a light amount of light from the light source. A storage unit that stores a relationship between a control current and a light amount supplied to the light source; and a display unit that displays the display image by light from the light source based on the relationship between the control current and the light amount stored in the storage unit. And a control unit for controlling the control current. When the optical scanning unit scans an area outside the display image, the control unit detects the light amount of the scanned light by the light amount detection unit, and the control stored in the storage unit based on the detected light amount Update the relationship between current and light intensity.

Description

  The present invention relates to an image display device, an in-vehicle system, and an image display method.

  Laser scanning projectors are used in in-vehicle HUD devices and the like having a navigation function for car drivers because of their good visibility that can realize clear contrast. In order to reduce discomfort caused by a viewer such as a driver in such a HUD device, a dimming technique is known in which the luminance of a display image of the HUD device is changed according to external light.

  Patent Document 1 discloses a laser beam display device for ensuring reproducibility of a video signal regardless of the intensity of external light in an in-vehicle HUD device. The laser beam display device of Patent Document 1 has a plurality of light control LUTs (look-up tables) that store the light control amount using the gradation level as an index for each of a plurality of light control steps. According to the technique of Patent Document 1, the brightness of laser light is dimmed according to a dimming setting and a video signal that are input with reference to a dimming LUT stored in advance.

  An object of the present invention is to provide an image display device capable of displaying a display image having various gradations with high accuracy.

  An image display apparatus according to an aspect of the present invention includes a light source that emits light, a light scanning unit that draws a display image by scanning a predetermined scanning region with light from the light source, and a light amount of light from the light source. Based on the relationship between the control current and the light amount stored in the storage unit, the storage unit for storing the relationship between the control current and the light amount supplied to the light source, A control unit that controls the control current so as to display the display image with light, and the control unit scans an area outside the display image when the light scanning unit scans an area outside the display image. The light amount is detected by the light amount detection unit, and the relationship between the control current and the light amount stored in the storage unit is updated based on the detected light amount.

  ADVANTAGE OF THE INVENTION According to this invention, the image display apparatus which can display the display image which has a various gradation with high precision can be provided.

FIG. 6 is a front view showing an example of a virtual image displayed in a superimposed manner on a front landscape of the host vehicle 301 that can be seen by the driver 300 through the windshield 302 in the automobile HUD device 200 according to the embodiment of the present invention. It is a partially broken schematic side view schematically showing an example of the internal configuration of an automobile equipped with the automobile HUD device 200 according to the embodiment. FIG. 3 is a block diagram schematically showing an example of the internal configuration of an optical system 230 of the automobile HUD device 200 of FIG. 2. FIG. 4 is a block diagram illustrating an internal configuration example of a light source unit 220 of the optical system 230 in FIG. 3. It is a block diagram which shows the example of an internal structure of the control system 250 of the HUD apparatus 200 for motor vehicles of FIG. It is a block diagram which shows the example of schematic structure of the HUD apparatus 200 for motor vehicles of FIG. 2, and a peripheral device. 5 is a flowchart illustrating an example of a light amount table update process executed by a control system 250 according to the first embodiment. 5 is a flowchart illustrating an example of a light amount table switching process executed by a control system 250 according to the first embodiment. FIG. 4 is a diagram illustrating an example of a scanning region 600 by the optical scanning device 208 of FIG. 3. It is a figure which shows an example of the relationship between the light quantity acquired in the light quantity table update process of FIG. 7A, and control current. It is an example of the timing chart of each signal in the light quantity table update process of FIG. 7A. It is a figure which shows the example of a relationship between the gradation of the display image and light quantity in the light quantity table update process of FIG. 7A. It is a figure which shows the example of a relationship between the gradation of the display image in the light quantity table update process of FIG. 7A, and control current. It is a figure which shows the example of a relationship between the light quantity in different pulse drive conditions, and control current. 10 is a flowchart illustrating an example of a light amount table update process executed by a control system 250 according to the second embodiment. 10 is a flowchart illustrating an example of a light amount table switching process executed by a control system 250 according to the second embodiment.

  According to the embodiment described below, a display image having various gradations is displayed with high accuracy by avoiding a deterioration in image quality of a display image due to a color shift or the like caused by characteristics inherent to a laser light source such as temperature change and aging deterioration. be able to.

  Hereinafter, embodiments according to the present invention will be described with reference to the drawings. In the following description of each embodiment, the same components are denoted by the same reference numerals, and description thereof will be omitted as appropriate.

  Hereinafter, an exemplary hardware configuration of an automotive HUD device 200 (hereinafter simply referred to as a HUD device 200) common to the first and second embodiments will be described.

  FIG. 1 is a front view showing an example of a virtual image displayed on the HUD device 200 so as to be superimposed on the front scenery of the host vehicle 301 seen from the driver 300 through the windshield 302. FIG. 2 is a partially broken schematic side view schematically showing an example of the internal configuration of an automobile equipped with the HUD device 200 according to each embodiment. FIG. 3 is a block diagram schematically showing an example of the internal configuration of the optical system of the HUD device 200 of FIG. FIG. 4 is a block diagram illustrating an internal configuration example of the light source unit 220 of the optical system 230 of FIG.

  In FIG. 2, the HUD device 200 according to each embodiment is installed, for example, in a dashboard of a host vehicle 301 that is a traveling body as a moving body. The projection light L, which is image light emitted from the HUD device 200 in the dashboard, is reflected by the windshield 302 as a light transmitting member and travels toward the driver 300 who is a viewer. Accordingly, the driver 300 can visually recognize a HUD display image such as a route navigation image described later as a virtual image G. A combiner as a light transmitting member may be installed on the inner wall surface of the windshield 302 so that the driver can visually recognize a virtual image by the projection light L reflected by the combiner.

  A front photographing camera 110 that captures a front image including the display information of the HUD device 200 reflected on the front glass 302 and the background thereof that can be seen through the front glass 302, and ambient light around the display image are displayed on the top of the front glass 302. An ambient light sensor 150 that detects lightness (or illuminance) and chromaticity is provided.

  In each embodiment, the optical system of the HUD device 200 is designed so that the distance from the driver 300 to the virtual image G is 5 m or more. In the conventional general automobile HUD device, the distance from the driver 300 to the virtual image is about 2 m. The driver is usually gazing at an infinite point in front of the vehicle or gazing at a preceding vehicle several tens of meters away. When a driver who focuses on such a distant place wants to visually recognize a virtual image 2 meters ahead, the focal length differs greatly, and thus the eye lens needs to be moved greatly. Therefore, the focus adjustment time until focusing on the virtual image becomes long, and it takes time to recognize the contents of the virtual image, and there may be a problem that the eyeball of the driver 300 is easily fatigued. In addition, it may be difficult for the driver to notice the contents of the virtual image and it is difficult to appropriately provide information to the driver by the virtual image.

  If the distance to the virtual image G is 5 m or more as in each embodiment, the amount of movement of the lens of the eyeball is reduced compared to the prior art, and the focus adjustment time for the virtual image G is shortened to recognize the contents of the virtual image G early. It is possible to reduce the fatigue of the eyeball of the driver 300. Furthermore, it becomes easy for the driver to notice the contents of the virtual image G, and it becomes easy to appropriately provide information to the driver by the virtual image G. If the distance to the virtual image G is 5 m or more, it is possible to focus on the virtual image G with almost no converging movement of the eyeball. Therefore, the effect of using the motion parallax to perceive a sense of distance (change in perceived distance) or a sense of depth (difference in perceived distance) is suppressed from fading due to the eyeball's convergence motion. Therefore, the information perception effect of the driver using the sense of distance and the sense of depth of the image can be effectively exhibited.

  The HUD device 200 of FIG. 3 includes a light source unit 220 in which the light source device is unitized by an optical housing in the optical system 230. The HUD device 200 further includes a light amount adjusting unit 207, an optical scanning device 208 as an optical scanning unit, a free-form curved mirror 209, a microlens array 210 as a light diverging member, and a projection mirror 211 as a light reflecting member. Including.

  The light source unit 220 in FIG. 4 includes red, green, and blue laser light sources 201R, 201G, and 201B, coupling lenses 202R, 202G, and 202B and apertures 203R, 203G, and 203B provided for each laser light source, and a combining element 204. Including. The light source unit 220 further includes a meniscus lens 205 and a power monitor PD (photodiode) 206.

  The laser light sources 201B, 201R, and 201G in FIG. 4 include light source elements having one or a plurality of light emission points such as LD (semiconductor laser element). The laser light sources 201B, 201R, and 201G emit light beams having different wavelengths λB, λR, and λG, such as wavelengths λB = 445 nm, λR = 640 nm, and λG = 530 nm, respectively. The light beams from the laser light sources 201B, 201R, and 201G are incident on the apertures 203B, 203R, and 203G through the coupling lenses 202B, 202R, and 202G, respectively, are shaped according to the aperture shape of each aperture, and are incident on the combining element 204. To do. The aperture shapes of the apertures 203B, 203R, and 203G are set according to the divergence angle of the light beam, and can be set to various shapes such as a circle, an ellipse, a rectangle, and a square.

  The combining element 204 includes a plurality of dichroic mirrors 204B, 204R, and 204G. Each of the dichroic mirrors 204B, 204R, and 204G has a plate shape or a prism shape, and is disposed to face the apertures 203B, 203R, and 203G, respectively. The dichroic mirror 204B reflects light in the vicinity of the wavelength λB, the dichroic mirror 204R transmits light in the vicinity of the wavelength λB and reflects light in the vicinity of the wavelength λR, and the dichroic mirror 204G transmits the light in the vicinity of the wavelength λG and transmits the light in the wavelength λB Reflects light in the vicinity and in the vicinity of the wavelength λR. Due to such optical characteristics, the combining element 204 combines the light beams from the laser light sources 201B, 201R, and 201G. The combined light flux is emitted to the optical scanning device 208 in FIG. 3 through the meniscus lens 205 having a concave surface facing the reflection surface of the optical scanning device 208.

  Further, the dichroic mirror 204G of the combining element 204 has an optical characteristic that reflects part of the light near the wavelength λG and transmits part of the light near the wavelength λB and the wavelength λR. Due to this optical characteristic, the combining element 204 emits a part of the light from each of the laser light sources 201B, 201R, and 201G to the power monitor PD 206. As will be described in detail later, the power monitor PD 206 is a photodiode for detecting the amount of laser light emitted from the laser light sources 201B, 201R, and 201G, and is an example of a light amount detector in the HUD device 200.

  The HUD device 200 according to each embodiment projects an intermediate image formed on the microlens array 210 onto the windshield 302 of the host vehicle 301, so that an enlarged image of the intermediate image is given to the driver 300 as a virtual image G. Make it visible. The respective color laser beams emitted from the laser light sources 201R, 201G, and 201B are combined in the light source unit 220, and the combined laser beams are adjusted in light amount by the light amount adjusting unit 207, and then scanned by the mirror of the optical scanning device 208. Is deflected two-dimensionally. The scanning light L ′ deflected two-dimensionally by the scanning operation of the optical scanning device 208 is reflected by the free-form surface mirror 209 and corrected for distortion, and then condensed on the microlens array 210 to draw an intermediate image. .

  In each embodiment, the microlens array 210 is used as a light diffusing member that individually diverges and emits a light beam for each pixel of the intermediate image (one point of the intermediate image), but other light diffusing members are used. May be. Further, as a method of forming the intermediate image G ′, a method using a liquid crystal display (LCD) or a fluorescent display tube (VFD) may be used. However, the laser scanning method is preferable for displaying a large virtual image G with high luminance.

  Further, in a method using a liquid crystal display (LCD), a fluorescent display tube (VFD) or the like, a slight amount of light is applied to the non-image portion in the display area where the virtual image G is displayed, and this is completely blocked. Is difficult. For this reason, it is conceivable that the visibility of the forward scenery of the host vehicle 301 through the non-image portion is poor. On the other hand, according to the laser scanning method, for the non-image portion in the display area of the virtual image G, the non-image portion is completely irradiated with light by turning off the laser light sources 201R, 201G, and 201B. Can be blocked. Therefore, it is possible to avoid a situation in which the visibility of the front landscape of the host vehicle 301 through the non-image portion is reduced by the light emitted from the HUD device 200, and the visibility of the front landscape can be improved.

  Furthermore, when the level of warning is increased by increasing the brightness of the warning image for warning the driver in stages, only the brightness of the warning image among the displayed images is increased in stages. Display control is required. As described above, the laser scanning method is also preferable when performing display control for partially increasing the luminance of a partial image. In a method using a liquid crystal display (LCD), a fluorescent display tube (VFD), etc., the brightness of images other than the displayed warning image is also increased. Therefore, there may be a case where the brightness difference between the warning image and the other images cannot be widened, and the effect of increasing the degree of warning by increasing the brightness of the warning image in stages cannot be obtained sufficiently. Because.

  The optical scanning device 208 performs a scanning operation for tilting the mirror in the main scanning direction and the sub-scanning direction by a known actuator driving system such as a MEMS (Micro Electro Mechanical System), and deflects the laser light incident on the mirror two-dimensionally. (Raster scan). The drive control of the mirror is performed in synchronization with the light emission timings of the laser light sources 201R, 201G, and 201B. The optical scanning device 208 is not limited to the configuration described above. For example, a mirror system including two mirrors that swing or rotate around two axes orthogonal to each other may be used.

  FIG. 5 is a block diagram showing an example of the internal configuration of the control system 250 of the HUD device 200 of FIG. In FIG. 5, the control system 250 of the HUD device 200 includes an FPGA (Field Programmable Gate Array) 251, a CPU (Central Processing Unit) 252, a ROM (Read-Only Memory) 253, and a RAM (Random Access Memory 4). , I / F) 255, bus line 256, LD driver 257, and MEMS controller 258.

  The FPGA 251 controls the operation of the laser light sources 201R, 201G, and 201B of the light source unit 220 by the LD driver 257, and controls the scanning operation of the MEMS 208a of the optical scanning device 208 by the MEMS controller 258. The LD driver 257 performs pulse modulation such as PWM (Pulse-Width Modulation), PAM (Pulse-Amplitude Modulation), or PFM (Pulse-Frequency Modulation), and each laser light source 201R, 201G, Drive 201B.

  The CPU 252 controls each function of the HUD device 200. The ROM 253 stores various programs such as an image processing program executed by the CPU 252 to control each function of the HUD device 200. The RAM 254 is used as a work area for the CPU 252.

  The I / F 255 is an interface for communicating with an external controller or the like, and is connected to, for example, the vehicle navigation device 400, various sensor devices 500, and the like via a CAN (Controller Area Network) of the host vehicle 301. Further, the I / F 255 is connected to a front photographing camera 110 that photographs a front image including display information of the HUD device 200 reflected on the windshield 302 and the background seen through the windshield 302. An ambient light sensor 150 that detects the brightness (or illuminance) and chromaticity of ambient light is also connected to the I / F 255.

  As will be described in detail later, the control system 250 executes the light amount table update processing (see FIGS. 7A and 14A) according to the first and second embodiments, thereby reducing the luminance of the display image displayed by the HUD device 200. Correct to maintain white balance.

  FIG. 6 is a block diagram showing a schematic configuration example of the HUD device 200 and peripheral devices of FIG. In each embodiment, the vehicle navigation apparatus 400, the sensor apparatus 500, etc. are provided as an information acquisition part which acquires the driver | operator provision information provided to the driver | operator 300 by the virtual image G. The HUD device 200 mainly includes an optical system 230 which is an example of an image light projection unit as an image display unit, and a control system 250 as a display control unit. The HUD device 200 and various peripheral devices including the information acquisition unit are included in an in-vehicle system mounted on the host vehicle 301.

  As the vehicle navigation device 400 according to each embodiment, a known vehicle navigation device mounted on an automobile or the like can be widely used. Information for generating a route navigation image to be displayed as a virtual image G is output from the vehicle navigation device 400, and this information is input to the control system 250. For example, as shown in FIG. 1, the number of lanes (travel lanes) on the road on which the host vehicle 301 is traveling, the distance to the point where the next route should be changed (right turn, left turn, branch, etc.), and the next route change An image indicating information such as a direction to perform is included. These pieces of information are input from the vehicle navigation device 400 to the control system 250. As a result, under the control of the control system 250, the display is performed as follows by the HUD device 200. That is, route navigation images such as a travel lane instruction image 711, an inter-vehicle distance presentation image 712, a route designation image 721, a remaining distance image 722, and an intersection name image 723 are displayed in the upper display area A.

  In the image example shown in FIG. 1, an image indicating road specific information (road name, speed limit, etc.) is displayed in the lower display area B. This road specific information is also input from the vehicle navigation device 400 to the control system 250. The control system 250 displays the road name display image 701, the speed limit display image 702, the overtaking prohibition display image 703, and the like corresponding to the road specific information in the lower display area B by the HUD device 200.

  6 includes one or more sensors for detecting various types of information indicating the behavior of the host vehicle 301, the state of the host vehicle 301, the situation around the host vehicle 301, and the like. Sensing information for generating an image to be displayed as a virtual image G is output from the sensor device 500, and this sensing information is input to the control system 250. For example, in the image example shown in FIG. 1, a vehicle speed display image 704 (character image “83 km / h” in FIG. 1) indicating the vehicle speed of the host vehicle 301 is displayed in the lower display area B. Therefore, vehicle speed information included in the CAN information of the host vehicle 301 is input from the sensor device 500 to the control system 250, and a character image indicating the vehicle speed is displayed in the lower display area B by the HUD device 200 under the control of the control system 250. Is done.

As sensors included in the sensor device 500, other than the sensors that detect the vehicle speed of the host vehicle 301, for example, the following sensors (1) to (4) may be mentioned.
(1) A laser radar device or an imaging device that detects the distance from other vehicles, pedestrians, and buildings (guardrails, utility poles, etc.) existing around the vehicle 301 (front, side, rear), outside the vehicle Sensor for detecting environmental information (outside temperature, brightness, weather, etc.) (2) Sensor for detecting driving operation (brake scanning, accelerator opening / closing degree, etc.) of driver 300 (3) Fuel of own vehicle 301 Sensor for detecting the remaining amount of fuel in the tank (4) Sensor for detecting the state of various in-vehicle devices such as the engine and battery The sensor device 500 including such a sensor detects information and sends it to the control system 250 Thus, the information can be displayed as a virtual image G by the HUD device 200 and provided to the driver 300.

  Next, the virtual image G displayed by the HUD device 200 will be described. In the HUD device 200 in each embodiment, the driver providing information provided to the driver 300 by the virtual image G may be any information as long as the information is useful for the driver 300. In each embodiment, driver-provided information is roughly divided into passive information and active information.

  Passive information is information passively recognized by the driver 300 at a timing when a predetermined information provision condition is satisfied. Therefore, information provided to the driver 300 at the setting timing of the HUD device 200 is included in the passive information, and information having a certain relationship between the timing at which the information is provided and the content of the information is passive information. include.

  Examples of the passive information include information related to safety during driving, route navigation information, and the like. As information related to safety during driving, information on the distance between the host vehicle 301 and the preceding vehicle 350 (vehicle distance presentation image 712), information on the urgency related to driving (emergency operation instruction for instructing the driver to perform an emergency operation) Warning information such as information or alert information). The route navigation information is information for guiding a travel route to a preset destination, and may be information provided to the driver by a known vehicle navigation device.

  The route navigation information includes travel lane instruction information (travel lane instruction image 711) for instructing a travel lane to travel at the nearest intersection, and a route change operation at an intersection or branch point where the course should be changed from the next straight direction. For example, route change operation instruction information to be instructed. As route change operation instruction information, route designation information (route designation image 721) for designating which route should be taken at an intersection or the like, remaining distance information (remaining distance image 722) to an intersection or the like performing the route change operation There is name information such as an intersection (name image 723 such as an intersection).

  The active information is information that is actively recognized by the driver 300 at a timing determined by the driver himself. The active information is sufficient information if provided to the driver at a timing desired by the driver 300, for example, information that has low or no relationship between the timing at which the information is provided and the content of the information. Is included in the active information.

  The active information is information that the driver 300 acquires at a timing desired by the driver 300, and is information that is continuously displayed for a long period of time or constantly. For example, specific information of the road on which the host vehicle 301 is traveling, vehicle speed information of the host vehicle 301 (vehicle speed display image 704), current time information, and the like can be given. As specific information of the road, for example, the road name information (road name display image 701), restriction content information such as the speed limit of the road (speed limit display image 702, overtaking prohibition display image 703), and other related to the road Information useful for the driver 300 is listed as information.

  In each embodiment, the passive information and the active information roughly classified in this way are displayed in the corresponding display areas where the virtual image G can be displayed. Specifically, in each embodiment, two display areas are set up and down, and a passive information image mainly corresponding to passive information is displayed in the upper display area A, and the lower display area B is displayed in the lower display area B. An active information image corresponding to active information is mainly displayed. When a part of the active information image is displayed in the upper display area A, the active information image is displayed in such a manner that priority is given to the visibility of the passive information image displayed in the upper display area A.

  In each embodiment, a stereoscopic image expressed using stereoscopic vision is used as the virtual image G to be displayed. Specifically, perspective images expressed by perspective are used as the inter-vehicle distance presentation image 712 and the travel lane instruction image 711 displayed in the upper display area A.

  Specifically, the distance drawn by the perspective method so that the length of the five horizontal lines included in the inter-vehicle distance presentation image 712 is shortened toward the upper side and the inter-vehicle distance presentation image 712 is directed to one vanishing point. Legal images. In particular, in each embodiment, the inter-vehicle distance presentation image 712 is displayed so that the vanishing point is determined in the vicinity of the gazing point of the driver 300, so that the driver 300 during driving can feel the depth of the inter-vehicle distance presentation image 712. Easy to perceive. Further, in each embodiment, a perspective image is used in which the thickness of the horizontal line is made thinner toward the upper side and the luminance of the horizontal line is made lower toward the upper side. This makes it easier for the driver 300 during driving to perceive a sense of depth in the inter-vehicle distance presentation image 712.

In the above, the hardware configuration example of the HUD device 200 used in the first and second embodiments has been mainly described. In each embodiment described below, the following hardware elements are used.
(1) In the first embodiment, the light amount table 253t in the ROM 253 and the ambient light sensor 150 (however, a sensor that detects only illuminance may be used). Therefore, the front photographing camera 110 may not be provided.
(2) In the second embodiment, the light amount table 253t and the front photographing camera 110 in the ROM 253 are used. Therefore, the ambient light sensor 150 may not be provided.

[Embodiment 1]
In the description of the first embodiment, a method of displaying a display image with an appropriate luminance and without color misalignment in the HUD apparatus 200 of FIG. Hereinafter, the present embodiment will be described with reference to the drawings. FIG. 7A is a flowchart illustrating an example of a light amount table update process executed by the control system 250 according to the first embodiment. FIG. 8 is a diagram showing an example of a scanning region 600 by the optical scanning device 208 of FIG.

  In the present embodiment, in order to make a display image easier to see for a viewer such as the driver 300 under an environment of external light that changes between daytime and nighttime, the display image is displayed using, for example, the ambient light sensor 150 of FIG. Adjust the brightness. In this case, in order to widen the dynamic range of the luminance of the display image, a low-luminance display image is realized by pulse driving of the laser light sources 201R, 201G, and 201B. Hereinafter, according to the illuminance or brightness of the external light, the setting conditions for appropriately setting the pulse width or pulse drive frequency of the laser light sources 201R, 201G, 201B to values suitable for the illuminance or brightness of the external light are referred to as “pulse drive conditions”. " The control system 250 detects the illuminance or lightness of the external light by the ambient light sensor 150. For example, at night when the illuminance or lightness of the external light is low, the display image is compared with the daytime when the illuminance or lightness of the external light is high. The pulse driving conditions for lowering the brightness of the are selected. As a result, the display image is easy to see for a viewer such as the driver 300. The light quantity table 253t for each pulse driving condition is stored in advance in the ROM 253, for example.

  At the time of pulse driving of the laser light sources 201R, 201G, and 201B, the white balance of the display image is likely to be lost due to differences in rising characteristics of the laser light sources. For this reason, in this embodiment, the light amount table 253t indicating the relationship between the control current supplied to the laser light sources 201R, 201G, and 201B and the gradation for each pulse driving condition is used, and the light amount table update process of FIG. Thus, the light quantity in the display image is corrected by updating the light quantity table 253t as needed. Further, since the white balance of the display image may be lost due to the difference in temperature characteristics of the laser light sources 201R, 201G, and 201B, a case where a color shift occurs in the display image during use of the HUD device 200 is assumed. Therefore, in the present embodiment, in the light amount table update process of FIG. 7A, the light amount table 253t is periodically updated, for example, while the display image is displayed.

  FIG. 8 shows a scanning area 600 scanned by the optical scanning device 208 of FIG. 3 when displaying a display image of one frame. In FIG. 8, the X direction is the main scanning direction, and the Y direction is the sub scanning direction. In the present embodiment, in order to make it possible to update the light amount table 253t while displaying a display image, the scanning area 600 is outside the effective image display area 610 for allowing the viewer to visually recognize the display image. A light amount acquisition area 620 for acquiring the light amount of each laser light source is provided. In the light amount table update process of FIG. 7A, the light amount table 253t is appropriately updated by acquiring the real-time light amount of each laser light source using the light amount acquisition region 620, and the display image can be displayed with high accuracy.

  In FIG. 8, the light amount acquisition region 620 is illustrated in the Y direction of the effective image display region 610, that is, above the light amount acquisition region 620, but is not limited to this example. It may be in the reverse direction, that is, in the lower direction or in the X direction. Further, the projection light L that scans the light amount acquisition region 620 may be shielded so that the viewer can see the display image in the effective image display region 610 but not the light amount acquisition region 620. The projection light L that scans the light quantity acquisition region 620 can be blocked by appropriately setting an optical system on the optical path in FIG. For example, as shown in FIG. 3, a light blocking member 212 may be provided on the optical path of the projection light L in the optical system 230. The light blocking member 212 can block the projection light L when the projection light L scans the light amount acquisition region 620 so that the light amount acquisition region 620 is not reflected on the windshield 302.

  Hereinafter, the light amount table update process shown in the flowchart of FIG. 7A will be described with reference to FIGS. 7A, 8, and 9. FIG. 9 is a diagram illustrating a relationship example between the light amount acquired in the light amount table update process of FIG. 7A and the control current. 7A is executed by the control system 250 in FIG. 5 when the HUD device 200 is activated and during display of a display image. The HUD device 200 may be activated when, for example, the ignition of the host vehicle 301 is on.

  In step S1 of FIG. 7A, the control system 250 determines whether or not the current time is the start of this process, for example, when the HUD device 200 is activated. When the control system 250 determines that the current time is the start time of the HUD device 200, which is the start time of this processing (YES in step S1), the control system 250 reads the light amount table 253t for each pulse driving condition from the ROM 253 (step S2). The ROM 253 previously stores a light amount table 253t including initial value data at the time of rising of each laser light source for each pulse driving condition. By using the light amount table 253t including the initial value data at the time of rising of each laser light source read out in step S2, it is possible to shorten the period for correcting the luminance and color shift at the time of activation.

  Next, the control system 250 acquires the total number N of pulse driving conditions based on the light amount table 253t for each pulse driving condition read from the ROM 253 (S3), and proceeds to step S4. If the control system 250 determines in step S1 that the current time is not the time of starting the HUD device 200, which is the start of this process (NO in step S1), the control system 250 proceeds to step S4.

  In step S4, the control system 250 selects one pulse driving condition from the total number N of pulse driving conditions (step S4). Next, the control system 250 determines a target light amount based on the selected pulse driving condition (step S5). The target light amount is a light amount realized by a control current that realizes the maximum gradation under the selected pulse driving condition. For example, the control system 250 determines the target light amount according to the duty ratio in the pulse driving condition by PWM described above.

  Next, the control system 250 gradually changes the control current of each of the laser light sources 201R, 201G, and 201B during scanning of the light quantity acquisition region 620 in FIG. 8, and acquires the light quantity detected by the power monitor PD 206 during the scanning period. (Step S6). In step S6, the CPU 252 in the control system 250 in FIG. 5 sets the FPGA 251 and the LD driver 257 so as to perform an operation based on the selected pulse driving condition during the scanning period of the light amount acquisition region 620. The FPGA 251 synchronizes the LD driver 257 and the MEMS controller 258. The LD driver 257 sends a control current to the laser light sources 201R, 201G, and 201B so as to pulse-modulate the laser light by switching the pulse driving conditions between the scanning period of the effective image display area 610 and the scanning period of the light amount acquisition area 620 in FIG. Supply.

  In FIG. 9, the target light amount P1 is set to, for example, target light amount P1 = 100 mW in step S5. In step S6, the control system 250 gradually increases the control current from the vicinity of the laser oscillation threshold of 100 mA, and simultaneously detects the amount of light detected by the power monitor PD 206. The control system 250 increases the control current until the detected light amount reaches the target light amount P1, and shows the relationship between the light amount until reaching the target light amount P1 and the current value of the control current as shown in FIG. A characteristic curve C1 is acquired. In the example of FIG. 9, the target light amount P1 is reached at the control current I1 = 200 mA.

  The process of step S6 described above is performed for each scanning period of the light amount acquisition region 620 in one or a plurality of frames, as will be described in detail later. In the present embodiment, the control system 250 sequentially performs the process of step S6 in FIG. 7A described above for each of the laser light sources 201R, 201G, and 201B.

  Next, the control system 250 updates the corresponding light quantity table 253t based on the relationship between the light quantity up to the target light quantity obtained in step S6 and the control current (step S7). The light quantity table 253t updated in step S7 is the light quantity table 253t corresponding to the pulse driving condition selected in step S4. The light amount table 253t is updated by associating the light amount for each gradation with the control current as will be described in detail later with reference to FIGS. The update result light quantity table 253t is stored in the RAM 254, for example.

  Next, the control system 250 determines whether or not the updated number of light quantity tables has reached the total number N of pulse driving conditions (step S8). If the control system 250 determines that the number of updated light quantity tables has not reached the total number N of pulse drive conditions (NO in step S8), the control system 250 returns to step S4 to select an unupdated pulse drive condition, and the steps after step S5 Repeat the process. On the other hand, if the control system 250 determines that the updated number of light quantity tables has reached the total number N of pulse drive conditions (YES in step S8), the process ends. In the present embodiment, the above processing is repeatedly executed at a predetermined cycle.

  FIG. 7B is a flowchart illustrating an example of a light amount table switching process executed by the control system 250 according to the first embodiment. The processing in FIG. 7B is executed by the control system 250 for each frame of the display image, for example.

  In step S101, the control system 250 determines whether the lightness (or illuminance) of the external light has changed according to the detection result of the lightness (or illuminance) of the ambient light (external light) around the display image by the ambient light sensor 150. Judging. The determination in step S101 can be made, for example, by determining whether the detection value of the ambient light sensor 150 has changed by a predetermined amount or more.

  If the determination result in step S101 is NO, the control system 250 ends the process, and if YES, the process proceeds to step S102.

  In step S102, the control system 250 selects a pulse driving condition corresponding to the brightness (or illuminance) of the external light after the change. Next, in step S103, the control system 250 switches the light amount table 253t used when displaying the display image to the light amount table 253t corresponding to the pulse driving condition selected in step S102.

Thereafter, the control system 250 displays the display image of the frame by controlling the control currents of the laser light sources 201R, 201G, and 201B using the light amount table 253t thus switched.
In this way, the light quantity table 253t is updated as needed to correct white balance by correcting fluctuations in the response characteristics of the laser light sources 201R, 201G, and 201B due to temperature changes. As a result, even when the pulse driving conditions are switched in accordance with the change in the external light, it is possible to display the display image with high accuracy and at an appropriate brightness without any color shift. The control system 250 controls the control current using a light amount table 253t that associates the light amount for each gradation with the control current of each laser light source 201R, 201G, 201B, thereby maintaining a desired gradation while maintaining white balance. And a display image having a color can be displayed.

  7A may be executed when the user of the HUD device 200 performs a predetermined operation.

  In the present embodiment, when it is determined that the number of tables updated in step S8 in FIG. 7A has reached the total number N of pulse driving conditions, the display image is displayed using the updated light amount table 253t. However, the present invention is not limited to this, and the display image may be displayed using the updated portion of the light amount table 253t as needed before reaching the total number N.

  Hereinafter, the operation timing of step S6 in FIG. 7A will be described with reference to FIG. FIG. 10 is a timing chart of each signal in the light amount table update processing of FIG. 7A. The timing chart (a) shows the generation timing of the synchronization signal in the control system 250. The timing chart (b) shows the generation timing of the drive signals SA and SB of each part of the control system 250 based on the synchronization signal of the timing (a). The timing chart (c) shows a change in the tilt state of the mirror due to the scanning operation of the MEMS 208a based on the drive signal SA of the timing chart (b). The timing chart (d) shows the generation timing of the PD signal during the period T1 of the timing chart (c). The timing chart (e) shows a change in the amount of light received by the power monitor PD 206 based on the PD signal of the timing chart (d).

  The synchronization signal in the timing chart (a) is a signal that synchronizes each section in the control system 250 of FIG. 5 for each frame of the display image. As shown in the timing chart (b), the generation timing of the drive signals SA and SB of each section is determined. It is set. The drive signal SA in the timing chart (b) is a drive signal that causes the MEMS 208a to perform a scanning operation in the sub-scanning direction. As shown in the timing chart (c), the scanning position by the MEMS 208a changes with the frame period in the Y direction, and the scanning position Y1 by the projection light L corresponds to the lower end of the light quantity acquisition region 620 in FIG.

  The PD signal in the timing chart (d) is a signal for controlling light reception by the power monitor PD 206. As shown in the timing chart (e), the control system 250 controls the power monitor PD 206 so as to repeatedly receive light with the number of times of light reception 621 by the PD signal in the timing chart (d) in the period T1 of the timing chart (c). The amount of light received by the power monitor PD 206 during the capture period T2 is captured. Thereby, the control system 250 acquires, for example, the amount of light for 40 points on the characteristic curve C1 in FIG. 9 during the period T2 in one frame.

  In step S6 of FIG. 7A, the control system 250 acquires the amount of light for each of the laser light sources 201R, 201G, and 201B and for each pulse driving condition over a plurality of frames. During the light quantity acquisition, the control system 250 drives the laser light sources 201R, 201G, and 201B with respect to the effective image display area 610 in FIG. 8 under pulse drive conditions set separately from the pulse drive conditions for which the light quantity is to be acquired. Display the display image. Thereby, the light quantity table 253t can be updated efficiently while the display image is displayed.

  Hereinafter, the update method of the light quantity table 253t in step S7 of FIG. 7A will be described with reference to FIGS.

  FIG. 11 is a diagram illustrating a relationship example between the gradation of the display image and the light amount in the light amount table update processing of FIG. 7A. In order to express the display image in a smooth gray scale, the relational expression between the gradation and the light amount is not linear as shown in FIG. 11, but a predetermined γ value (a change in gradation and light amount in the display image) It is represented by a curve C2 having a ratio). In the present embodiment, information indicating the curve C2 is stored in advance in the ROM 253 as, for example, an arithmetic expression having a γ value correction coefficient or a data table of light amounts for each gradation.

  FIG. 12 is a diagram illustrating a relationship example between the gradation of the display image and the control current in the light amount table update process of FIG. 7A. In step S7 of FIG. 7A, the control system 250 newly adds gradation and control current as shown in FIG. 12 based on the information indicating the characteristic curve C1 between the light amount and control current in FIG. 9 and the curve C2 in FIG. The relationship curve C3 is calculated. In the present embodiment, information indicating the relationship curve C3 is stored as the light amount table 253t. Note that the information indicating the relationship curve C3 may be stored as an arithmetic expression indicating the relationship between the gradation or the light amount for each gradation and the control current.

  FIG. 13 is a diagram illustrating the relationship between the light amount and the control current under different pulse driving conditions. In the present embodiment, the number of light quantity tables corresponding to the total number N of pulse driving conditions is used to maintain the white balance related to the difference in the light reduction rate for each of the laser light sources 201R, 201G, and 201B by the pulse driving. 253t is created and updated.

  In FIG. 13, a characteristic curve C11 shows the characteristic of the light quantity with respect to the control current under continuous light emission, that is, a pulse driving condition with a duty ratio of 1, and a characteristic curve C12 shows the characteristic of the light quantity with respect to the control current under a pulse driving condition with a duty ratio of 0.5. Show. It is assumed that the light amount during pulse driving is measured by the integrated light amount in a predetermined period. Further, for convenience of explanation, hereinafter, it is assumed that FIG. 13 shows the characteristics of the laser light source 201R.

  In FIG. 13, when the control current I11 is supplied to the laser light source 201R during continuous light emission, the light amount becomes the light amount P11 based on the characteristic curve C11. Therefore, ideally, by supplying the control current I11 to the laser light source 201R when the duty ratio is 0.5, the light amount P12 that is half of the light amount P11 during continuous light emission should be obtained. However, when the responsiveness of the laser light source 201R is poor, it takes time to rise to a desired light amount during the light emission period, and the integrated light amount decreases. For this reason, in the example of the characteristic curve C12 in FIG. 13, the light amount when the control current I11 is supplied to the laser light source 201R is the light amount P13 smaller than the light amount P12.

  The responsiveness of each of the laser light sources 201R, 201G, and 201B is a characteristic unique to the laser, and varies depending on the temperature and current value. For this reason, if the same control current is supplied to the laser light sources 201R, 201G, and 201B before and after the switching of the pulse driving conditions, the white balance in the display image may be lost. Therefore, in the present embodiment, a light amount table 253t is created for each pulse driving condition of the laser light sources 201R, 201G, and 201B. Then, using the light amount table 253t, the relationship between the control current and the integrated light amount is individually managed for each of the laser light sources 201R, 201G, and 201B. For example, in the example of FIG. 13, the control current I12 that can obtain the light quantity P12 based on the characteristic curve C12 of the laser light source 201R is recorded in advance in the corresponding light quantity table 253t. By performing similar management for the other laser light sources 201G and 201B, it is possible to reliably maintain white balance under a pulse driving condition with a duty ratio of 0.5.

  In the present embodiment, the light amount table 253t indicating the relationship between the control current and the gradation in each pulse driving condition for each of the laser light sources 201R, 201G, and 201B as described above is updated as needed by the process described above with reference to FIG. 7A. The Thereby, even when there is a sudden change in external light and temperature, the HUD device 200 can display a display image with high accuracy while maintaining white balance.

  The HUD device 200 having the above-described configuration is an example of an image display device that displays a display image. The HUD device 200 includes laser light sources 201R, 201G, and 201B, an optical scanning device 208, a power monitor PD 206, a ROM 253, and a control system 250. The laser light sources 201R, 201G, and 201B emit light. The optical scanning device 208 draws a display image by scanning a predetermined scanning region 600 with light from the laser light sources 201R, 201G, and 201B. The power monitor PD 206 detects the amount of light from the laser light sources 201R, 201G, and 201B. The ROM 253 stores a light amount table 253t indicating the relationship between the control current supplied to the laser light sources 201R, 201G, and 201B and the light amount. Based on the light quantity table 253t, the control system 250 controls the control current so that the display image is displayed by the light from the laser light sources 201R, 201G, and 201B. The control system 250 acquires the light amount detected by the power monitor PD 206 when the optical scanning device 208 is scanning the external light amount acquisition region 620 of the display image, and stores the light amount stored in the ROM 253 based on the acquired light amount. The table 253t is updated.

  According to the HUD device 200, the light quantity table 253t stored in the ROM 253 is updated based on the light quantity detected by the power monitor PD 206 during the scanning of the light quantity acquisition region 620. Thereby, a display image having various gradations can be displayed with high accuracy.

[Embodiment 2]
In the first embodiment, the light amount table 253t for all pulse driving conditions is periodically updated, for example. In the second embodiment, it is predicted that the pulse driving condition is switched based on the surrounding environment such as a road. Then, before the predicted switching timing, the light amount table 253t corresponding to the pulse drive condition scheduled to be selected at the predicted switching timing is updated. Hereinafter, this embodiment will be described with reference to FIGS. 14A and 14B.

  FIG. 14A is a flowchart illustrating an example of a light amount table update process executed by the control system 250 according to the second embodiment. The HUD device 200 according to the present embodiment executes a light amount table update process in FIG. 14A and a light amount table change process in FIG. 14B instead of the light amount table update process in FIG. 7A and the light amount table change process in FIG. 7B.

  In step S11 of FIG. 14A, the control system 250 determines whether or not switching of the pulse driving condition is predicted. When the control system 250 determines that the switching of the pulse driving condition is not predicted (NO in step S11), the control system 250 repeats the process of step S11 at a predetermined cycle.

  The determination in step S11 is performed based on, for example, information acquired from various peripheral devices of the HUD device 200 in FIG. For example, it is possible to predict that the host vehicle 301 enters the tunnel, for example, by acquiring the road situation from the vehicle navigation device 400 of FIG. 6 or imaging the front of the host vehicle 301 with the front shooting camera 110. . In this case, in step S11, the control system 250 determines that switching of the pulse driving condition for reducing the luminance of the display image is predicted (YES in step S11), and proceeds to step S12.

  In step S12, the control system 250 estimates the pulse drive condition to be selected after switching, and in steps S13, S14, and S15 in FIG. 14A, the steps S5 and S6 in FIG. , S7, the process is terminated.

  FIG. 14B is a flowchart illustrating an example of a light amount table switching process executed by the control system 250 according to the second embodiment. The processing in FIG. 14B is executed by the control system 250 for each frame of the display image, for example.

  In step S111, the control system 250 determines whether to switch the pulse driving condition. The determination in step S111 is made based on information acquired from various peripheral devices of the HUD device 200 in FIG. 6, for example, as in step S11. For example, it is possible to determine that the host vehicle 301 enters the tunnel, for example, by acquiring road conditions from the vehicle navigation device 400 of FIG. 6 or capturing an image of the front of the host vehicle 301 with the front shooting camera 110. In this case, in step S111, the control system 250 determines to switch the pulse driving condition for reducing the luminance of the display image (YES in step S111), and proceeds to step S112.

  If the determination result in step S111 is NO, the control system 250 ends the process.

  In step S112, the control system 250 switches the light amount table 253t used when displaying the display image to the light amount table 253t of the pulse driving condition after switching determined in step S111.

  Thereafter, the control system 250 displays the display image of the frame by controlling the control currents of the laser light sources 201R, 201G, and 201B using the light amount table 253t thus switched.

Note that the control system 250 executes step S11 in FIG. 14A and step S111 in FIG. 14B as substantially the same processing, and then executes the update processing in steps S12 to S15 in FIG. 14A first. After the light quantity table 253t is updated in this way, the control system 250 switches the light quantity table 253t used when displaying the display image to the updated light quantity table 253t in step S112 of FIG. 15B. As a result, the control system 250 updates the light quantity table 253t to be selected immediately before the host vehicle 301 enters the tunnel, for example, and displays a display image using the updated light quantity table 253t in the tunnel.
Thus, since the light quantity table 253t to be selected is updated immediately before selection, a highly accurate display image can be displayed while maintaining white balance efficiently.

  In step S <b> 14, the control system 250 determines a pulse drive condition to be selected that is different from the pulse drive condition for displaying the display image when the optical scanning device 208 is scanning an area outside the display image. Is selected, and the laser beams from the laser light sources 201R, 201G, and 201B are pulse-modulated. At the same time, the control system 250 acquires the amount of light from the power monitor PD 206. Thereby, during display of the display image, the relationship between the light amount and the control current of the pulse drive condition different from the pulse drive condition for displaying the display image is acquired, and the light amount table 253t can be updated efficiently. .

  In the above processing, the control system 250 may estimate the timing for switching the pulse driving condition in step S112 in FIG. 14B when predicting in step S11. In this case, the control system 250 may start the processes after step S12 only before the period necessary for updating the light amount table from the estimated timing.

  As described above, the HUD device 200 according to the present embodiment is included in the in-vehicle system together with the vehicle navigation device 400 that acquires information to be provided to the vehicle driver by the display image. The HUD device 200 can determine whether to update the light amount table 253t based on the information acquired by the vehicle navigation device 400. In that case, by using information from the vehicle navigation device 400, the light amount table 253t can be updated efficiently.

[Modification]
The first embodiment and the second embodiment can be combined.

  That is, the control system 250 executes the processing of FIGS. 7A and 7B when the situation in which the determination result in step S11 of FIG. 14A is YES does not occur, for example, and the determination result in step S11 of FIG. When such a situation occurs, an “interrupt” is inserted into the processing of FIGS. 7A and 7B. As a result, the control system 250 executes the processes of FIGS. 14A and 14B. After the processing in FIGS. 14A and 14B is completed, the control system 250 returns to the processing in FIGS. 7A and 7B.

  Further, in each of the above embodiments, one power monitor PD 206 is used as the light amount detection unit in the light source unit 220 of FIG. However, the present invention is not limited to this example, and the power monitor PD 206 may not be installed in the light source unit 220. For example, the power monitor PD 206 may be installed outside the light source unit 220 so that the light beam after scanning by the optical scanning device 208 enters.

  Further, not only one power monitor PD 206 but also a plurality of power monitor PDs 206 may be used. For example, the optical path for installing each power monitor PD 206 may be determined so that the light beams from the laser light sources 201B, 201R, and 201G before being combined by the combining element 204 are detected separately. In this case, in step S6 of FIG. 7A and step S14 of FIG. 14A, the light amounts of the laser light sources 201B, 201R, and 201G of the respective colors can be detected simultaneously.

  In the above embodiments, the automotive HUD device 200 has been described as an example of the image display device according to the present invention. The image display device according to the present invention is not limited to the automotive HUD device 200 but may be a HUD device mounted on another moving body such as an aircraft. Moreover, when a viewer views a mobile body (for example, sushi in a sushi restaurant) through a predetermined window, the HUD device may display a display image through the window. Further, the image display device is not limited to the HUD device, and may be various HMD (head mounted display) devices, for example.

  The image display device, the in-vehicle system, and the image display method have been described above by way of the embodiments. However, the present invention is not limited to the above embodiments, and various modifications and improvements can be made within the scope of the present invention.

  This international application claims priority based on Japanese Patent Application No. 2006-023004 filed on February 9, 2016, and the entire contents of Japanese Patent Application No. 2006-023004 are incorporated herein by reference. Incorporate.

110: Front photographing camera 150 ... Ambient light sensor 200 ... Automotive HUD device 201R, 201G, 201B ... Laser light source 206 ... PD for power monitor
208: Optical scanning device 212 ... Shading member 250 ... Control system 251 ... FPGA
252 ... CPU
253 ... ROM
253t ... Light quantity table 254 ... RAM
300 ... Driver 301 ... Own vehicle 302 ... Windshield 400 ... Vehicle navigation device

JP 2014-132295 A

Claims (13)

A light source that emits light;
An optical scanning unit that draws a display image by scanning a predetermined scanning region with light from the light source;
A light amount detector for detecting the amount of light from the light source;
A storage unit for storing a relationship between a control current supplied to the light source and a light amount;
A control unit that controls the control current so as to display the display image by light from the light source based on the relationship between the control current and the light amount stored in the storage unit,
When the optical scanning unit scans an area outside the display image, the control unit detects the light amount of the scanned light by the light amount detection unit, and the control stored in the storage unit based on the detected light amount An image display device that updates the relationship between current and light intensity. The control unit controls the luminance of the display image by pulse-modulating light emitted from the light source,
The image display device according to claim 1, wherein the storage unit stores a relationship between the control current and the light amount for each pulse driving condition for pulse-modulating light emitted from the light source.   The image display device according to claim 2, wherein the relationship between the control current and the light amount is stored in the storage unit as a data table in which the control current and the light amount are associated with each pulse driving condition.   When the optical scanning unit scans an area outside the display image, the control unit performs pulse modulation on light emitted from the light source under a pulse driving condition different from a pulse driving condition for displaying the display image, and The image display device according to claim 2, wherein the light amount of the emitted light is detected by the light amount detection unit. The light source includes a plurality of light source elements that emit light of a plurality of colors having different wavelengths.
The image display device according to claim 1, wherein the control unit updates a relationship between the control current and the light amount for each light source element.   The image display device according to claim 1, wherein light for scanning an area outside the display image in the scanning area is shielded against a viewer who visually recognizes the display image.   When the optical scanning unit scans an external area of the display image, the control unit gradually increases the control current so that the amount of light to be scanned detected by the light amount detection unit reaches a predetermined light amount. The image display device according to claim 1, wherein the image display device is changed.   The image display device according to claim 1, wherein the light source emits light in a time-sharing manner for each pixel included in the display image based on the control current.   The control unit updates a relationship between the control current and the light amount stored in the storage unit during a period during which the display image is displayed, and displays the display image using the updated relationship. The image display device according to any one of 1 to 8.   The image display device according to claim 1, wherein the image display device is a head-up display that displays the display image on a windshield or a combiner of a vehicle. The image display device according to any one of claims 1 to 10,
An in-vehicle system including an information acquisition unit that acquires information to be provided to a driver of the vehicle by the display image.   The in-vehicle system according to claim 11, wherein the image display device determines whether or not to update the relationship stored in the storage unit based on the information acquired by the information acquisition unit. An image display method executed by an image display device,
Emitting light from a light source;
Scanning a predetermined scanning area with light from the light source to draw a display image;
Detecting the amount of light from the light source;
Storing the relationship between the control current supplied to the light source and the amount of light in a storage unit;
Controlling the control current to display the display image with light from the light source based on the stored relationship;
In the step of drawing the display image, when scanning an external area of the display image, the light amount of the light to be scanned is detected in the step of detecting the light amount, and is stored in the storage unit based on the detected light amount. An image display method including the step of updating the relationship between the control current and the light amount.

Images